Hydrophobically modified urethane thickeners (HEURs), which are produced from polyisocyanates and/or diisocyanates and glycols, are known as water soluble polymers containing hydrophobic groups. They are classified as associative thickeners and frequently used in latex paint formulations, where the hydrophobic groups adsorb to latex particle surfaces, giving rise to viscosity increase and desirable rheological characteristics over a wide range of shear rates. For example, U.S. Pat. No. 4,079,028 discloses HEUR thickeners.
However, open time, defined as the period of time in which a freshly applied wet paint film can be repainted over without impeding film formation or changing the physical appearance, is often problematic in latex paints.
It would therefore be an advance in the art of latex paint formulation to improve open time without producing a substantial negative effect on block resistance.